This application claims priority to European Application No. 01204916.9 filed Dec. 17, 2001 and European Application No. 02076366 filed Apr. 8, 2002. Each of the above-identified patent applications is hereby incorporated by reference as if fully disclosed herein.
1. Field of the Invention
This invention relates generally to a control system for operating and positioning a covering for an architectural opening, such as a window blind (e.g., a horizontal or vertical venetian blind). This invention particularly relates to a control system which includes a drive wheel for positioning a blind and an endless-loop operating cord, looped over the drive wheel, so that depending portions of the cord are on opposite sides of the drive wheel. This invention quite particularly relates to a safety device for such a control system that includes means for allowing the cord to be detached from the drive wheel when a generally downward force is exerted simultaneously on both depending portions of the cord.
2. Description of the Relevant Art
Means for releasing an endless-loop operating cord, in its entirety, from a control system of a window blind to ensure the safety of children that might become entangled in the cord are described in EP 0 869 254. The operating cord of EP 0 869 254 depends from opposite sides of a drive wheel but is not looped over the drive wheel. Rather, its operating cord is slidably attached to a mounting plate, which is releasably mounted on a mounting support, and the cord is kept in operative engagement with the lower half of the drive wheel by the mounting plate. When both depending portions of the cord are pulled at the same time, the mounting plate is released from the mounting support, thereby releasing the cord from the control system, thereby preventing possible injury to a child whose head may have become entangled in the cord.
However a drawback of the system of EP 0 869 254 is that since its operating cord is not slung over its drive wheel as is conventional, extra parts (at extra cost) must be provided to guide and maintain the cord in operative engagement with the drive wheel. These extra parts include the mounting plate, mounting support and a pair of pulleys located on the mounting plate. This system is also less energy efficient in positioning the blind, for a given effort pulling downwardly on one depending portion of the cord. Furthermore, the extra parts make failure of the control system, in routine operation of the blind, more likely.
In accordance with this invention, a cord-operated control system for a covering for an architectural opening is provided which includes:
a housing;
a first drive wheel that is operatively connected to a driven blind member, adapted to rotate in opposite directions to open and close the covering; the first drive wheel being adapted to rotate in opposite directions and being connected to the driven blind member, so that the driven blind member rotates with the first drive wheel;
a second drive wheel that is adapted to rotate in opposite directions within the housing, is rotatably connected to the housing and is operatively connected to the first drive wheel, so that the first drive wheel rotates with the second drive wheel;
an operating cord that is an endless loop and is looped over the second drive
wheel and has first and second, cord portions depending from opposite sides of the second drive wheel, whereby an axial pulling force on only the first cord portion causes the second drive wheel to rotate in a first direction and an axial pulling force on only the second cord portion causes the second drive wheel to rotate in an opposite second direction; and
release means for disconnecting, preferably non-destructively disconnecting, the second drive wheel from the first drive wheel only when there is an axial pulling force on both the first and second cord portions simultaneously.
In one advantageous embodiment, both the first and second drive wheels are rotatably mounted in the housing, and the release means are for dismounting the second drive wheel from the housing when there is the axial pulling force on both the first and second cord portions simultaneously.
In a further advantageous embodiment, the second drive wheel is operatively connected to the first drive wheel by a third drive wheel and an auxiliary operating cord. Advantageously, both the second drive wheel and the third drive wheel are rotatably mounted in the housing, the auxiliary drive cord is an endless loop and is looped over the first drive wheel and the third drive wheel to operatively connect them, and wherein, when the second drive wheel is rotated, it causes the third drive wheel to rotate, which in turn causes the auxiliary operating cord to drive the first drive wheel to rotate and thus causes the driven member to rotate.
In a still further advantageous embodiment, the release means are for disconnecting a lower portion of the housing with a drive wheel from an upper portion of the housing with another drive wheel. Advantageously, the release means comprises a releasable snap engagement arrangement between the lower and upper housing portions.
In a yet further advantageous embodiment, the second and third drive wheels are coaxially connected, and the release means are for disconnecting the coaxially-connected, second and third drive wheels. Advantageously, the release means comprises a releasable snap fit arrangement between the second and third drive wheels.
Further aspects of the invention will be apparent from the detailed description below of particular embodiments and the drawings thereof.